on IMAP authentication use e-mail address as email of NC user

[ghost]

Is your feature request related to a problem? Please describe.
It would be great when a user loged in via IMAP Auth, if not only his domain could be used as a group membership but if the e-mail address could also be used as the email address of the created nextcloud user.

Describe the solution you'd like
I'd like to have another boolean field in the configuration (config.php) of the backend to enable auto fill in of the given e-mail address.

'user_backends' => array( array( 'class' => 'OC_User_IMAP', 'arguments' => array( 'mail.foo.com', 993, 'ssl', 'example.com', false, true, true ), ), ),

Describe alternatives you've considered
Alternatively this entree could be created by default.

[violoncelloCH]

thanks for the suggestion... this was already requested in #12
If anyone is up for an implementation PRs are always welcome!